RE: 2-node RAC faster than 6-node!

  • From: "Bobak, Mark" <Mark.Bobak@xxxxxxxxxxxx>
  • To: "ebadi01@xxxxxxxxx" <ebadi01@xxxxxxxxx>, "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx>
  • Date: Wed, 2 Apr 2008 18:21:32 -0400

Hi Abdul,

It's tough to say, without really knowing what's going on.  I will say this, 
Rule #1 about adding hardware when faced w/ a performance problem is that if 
you add capacity to a non-bottleneck resource, there's a good chance you'll 
make the performance worse!

So, consider what your bottleneck really was, and whether you didn't make the 
bottleneck worse.  For example, what are you using for your interconnect?  What 
if that was already saturated, and adding extra nodes just put more load on the 
interconnect, further saturating it?

Total speculation, without knowing more about your system, I can't say....but 
it's just one hypothesis.


Mark J. Bobak
Senior Database Administrator, System & Product Technologies
789 E. Eisenhower, Parkway, P.O. Box 1346
Ann Arbor MI 48106-1346
+1.734.997.4059  or +1.800.521.0600 x 4059

ProQuest...Start here.

From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On 
Behalf Of A Ebadi
Sent: Wednesday, April 02, 2008 5:41 PM
To: oracle-l@xxxxxxxxxxxxx
Subject: 2-node RAC faster than 6-node!

We have an existing 4-node RAC cluster (v440's on Solaris & Oracle 10.2 w/ ASM) 
that was big time CPU-bound and application performance was suffering.  We 
added 2 new nodes(M5000's) to bring the total to 6 and the app performance 
actually went down significantly!   After messing around with it we found out 
that by taking the original 4 nodes out of the picture & only running on the 2 
new M5000's nodes things improved significantly - the app jobs started running 
in some cases 20X faster than ever!  We tested adding just a single node (v440) 
back in the mix and performance went way down immediately, so we decided to 
keep things running on just the 2 M5000's for now.

Any suggestions on identifying root cause as to why the adding of any nodes 
back to the picture slows things way down?   We have an SR opened with Oracle 
Support but nothing firm so far.


You rock. That's why Blockbuster's offering you one month of Blockbuster Total 
 No Cost.

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